Hiramekarei features a wide, flat blade with two curved indentations near its base, creating a sort of cross-guard. Two handles are connected to one another by a short length of cord, earning it the title of "twinsword" (双刀, sōtō). The overall sword looks like a flounder fish in shape. With its bandages wrapped around Hiramekarei, it looks similar to Samehada. Hiramekarei is apparently very heavy, as Chōjūrō tires easily when carrying it for extended periods of time.
Hiramekarei is capable of storing chakra. With the command "Hiramekarei Unleashing" (ヒラメカレイ解放, Hiramekarei Kaihō, Viz: Hiramekarei Release), the stored chakra is emitted from the holes at the tip of the blade. The chakra rapidly coats the sword and can be shaped into various weapons, such as a hammer or a long-sword. The more chakra that is stored in Hiramekarei, the larger the size of the manifested weapon. This discharge of chakra causes the bandages it is typically wrapped with to unravel.
It can also create a large amount of light blue, fish bone-like crystals that can inflict great damage and restrain the target's movements. Hiramekarei can also split into two swords, each with a single handle.
- This is the only one of the seven swords not to have a direct kanji translation, due to its name being written in katakana.
- Both hirame and karei are Japanese names for species of flounders. The flounders with their eyes on the left side of their body are called hirame (鮃, 平目, 比目魚), while those with their eyes on the right side are called karei (鰈). Befitting its name, Hiramekarei is shaped like these fish.
- When the previous generation of Seven Swordsmen is reincarnated, only Mangetsu Hōzuki and Fuguki Suikazan do not have swords, as both Hiramekarei and Samehada have modern owners. Because Fuguki is known to have been the wielder of Samehada, it is presumed that Mangetsu was the wielder of Hiramekarei.
- Kagura Karatachi was mentioned to be the successor of the Seven Ninja Swordsmen of the Mist group who is going to inherit Hiramekarei from Chōjūrō.